Combined digestion and refining of paper pulp



Y 7, 1959 J. c. SHOUVLIN ETAL- 2,893,909

COMBINED DIGESTION AND REFINING OF PAPER PULP Filed June 9. 1954 2Sheets-Sheet l INVENTOR. JOSEPH C. SHOUVLIN Y MHRVIN E'. GINBVEN B 1959J. c. SHOUVLIN ET AL 2893309 COMBINED DIGESTION AND REFINING OF PAPERPULP Filed June 9, 1954 2 Sheets-Sheet 2 INVEN TOR. JOSEPH C.Suouv1.m

Mnavm E.Gmnve- BMW W commits nroEsrroN RE'riNnsG or PAPER PULP Joseph C.Shbuvlin andMarvin E; Ginaven, Springfield,

Ohio, assignors to The Bauer Bros. Company, Springfield, "Ohio,acorporation-of Ohio Application Jlllle 9, 1954, SerialNo; 435,466

Claims. (Cl. 162-17) This invention relates to theart of pulping andrefining, and more particularly to methods and apparatus useful in thetreatment of 'afibrous material such as wood chips.

The object of the invention is to'simplify the construe-I tion as wellas the means and tmode" of operation of pulp refining systems, wherebysuch systems may'not only be economically manufactured, but will be moreefficient and satisfactory in use, adaptable tea-wide variety ofapplications,having relatively 'few parts and be unlikely to get out ofrepair.

It is a further object of the invention to introduce a generally newstep in the treatment 'of fibrousmaterials, it being proposed to subjectcooked but unrefined mate rial to action in a press so as to extract'residualcooking liquid from the material and to partly-defiber thematerial.

It is a further object, in this connection, to materially reduce thevolume of washwater required to neutralize and carry off acids andliquors" generated in the cooking process, it *being of course an'acce'ssory object in this regard to make. the disposal of the wasteliquids relatively easy and harmless:

A further object of the invention is to remove residual chemicals andacids from the cooked fibrousmaterial in a highly concentrated form inwhich it rn'ay have utility as a by-product of the refining-process.

Stillanother object of the invention'is to make the subsequentdefibering process (as in a 'disc type mill) easier and less costly inpower" consumption 'by effecting softening and preliminary defiberingof'the materialin" conjunction with the procms ofliquid extraction.

Still another object of the inv ention is to mount the cooker ordigester and press in close association with one another in such mannerthat the material from the cooker passes into the press without loss ofpressure and heat, it being proposed to substitute and make use of thepress itself for the conventional outlet control of the cooker.

Still further, it is an object of the invention to provide a method andapparatus for pulping and refining making use of a screw type pressdeveloping very high pressures, and making use of the heat generated bythese high pressures to soften the lignin, to aid the defiberingprocess.

A further object of the invention is the removal of residual liquids andmoisture in the fibrous material which obviates or reduces the need forWashing of the pulp fibers. Such moisture extraction also eliminatessubsequent drying operations in the case of semi-dry structural boardmanufacture. Y

Another object of the invention is to provide a generally new method ofand apparatus for defibering, including the use of a press forheatingand partly defibering a fibrous material and a refiner suppliedwithmaterial from saidpress. v

Stillanother object' of the' inve'ntion is to provide in the"'art ofpulping and refininga press for treating a fibrous materialbyapplyingcom ressive and" shearing some) Patented July 7, 19519 forces thereto,whereby to perform the several functions of liquid extraction, partialdefibering and heating.

A further object of the invention is to provide a pulp refining systempossessing the advantageous structural features, the inherentmeritorious characteristics and the mode of operation herein mentioned.

With the above primary and'other incidental objects in view as will morefully appear in the specification, the invention intended to beprotected by Letters Patent consists of the features of construction,the parts and combinations thereof, and the mode of operation, ashereinafter described or illustrated in the accompanying drawings, ortheir equivalents.

Referring to the drawings, wherein is found one but obviously notnecessarily the only embodiment of the invention,

Fig. 1 is a view, in diagram, of a part of a pulp mill installation, inaccordance with the illustrated embodiment of the present invention,

Fig. 2 is a view in longitudinal section, partly diagrammatic in form,of a screw press introduced in pulp mill work in accordance with theteaching of the instant inven tion, and

Fig. 3 is a view in cross section taken substantially along the line 33of Fig.2.

Like parts are indicated by similar characters of reference throughoutthe several views.

Referring to the drawings, the material tobe treated is introduced intothe inlet 11 of a conveyor unit 12, and carried by the unit 12 inoverlying relation to a digester tank 13. The material is then admittedto the upper end of such tank by way of a connector pipe 14, under control of valves 15 and 16 installed therein.

Steam is admitted to the digester 13 by way of a conduit 17, andchemicals by way of a conduit 18. An exhaust or pressure relief line 19communicates with the digester 13 by way of connector 14, and has acontrol valve 21 interposed therein.

At its lower end the digester 13 communicates, as through a connectorpipe 22, with the inlet end of a screw press 23, the opposite or outletend of which discharges through a conduit 24 to a disc type refiner 25.The digester 13 empties directly into the press, the connector 22 beingjoined at its one end in a fiuid tight manner to the digester andsimilarly connected at its opposite end to the body of the press.

Within the digester the fibrous material is in substance cooked at anelevated temperature on the order of 212 and higher, and at an elevatedpressure on the order of psi. and higher. A hydrolyzing action occurs,releasing acids. Various chemicals are added to control the rate ofreaction and to inhibit corrosion, and it has in the past been necessaryto extensively wash the cooked material to remove the acids and thechemicals. Practically all the end products utilizing the pulp materialare required to be substantially chemical free.

According to the present inventive concept, however, the pulp and thecooking liquor are allowed to pass. out of the bottom of the digesterand into the press 23 while still heated and under continuingsuper-atmospheric pressure. Within the press, in a manner to bedescribed, the admitted material is subjected to still greater pressuresand to shearing forces, resulting in an extraction of liquids and apartial defibering of the material.

The refiner 25 may, as indicated, be of the rotary disc type andperforms its usual function in mill operations exceptthat theefiiciency' and quality of its work are improved. Thus, the press 23represents a means for feeding pulp material to the machine 25 at acontrolled rate. T he'high pressures and shearing forces exerted on thematerial in the press further have the effect of softening the lignin infibrous material, and this in conjunction with the preliminarydefibering sible a better reduction of material in the refiner. and atless cost in power consumption.

Referring to Figs. 2 and 3, the press 23 is a screw press which includesbody members 26 supporting a cylinder 27 comprising a plurality of bars28 between which free and released liquid may escape from the press; Thecylinder 27 and aligned openings in the body 26 define a throughlongitudinal passage 29, one end of which communicates with a radialinlet opening 31 and the other end of which terminates in an outletopening 32. Flow through the latter is regulated by a sleeve 33longitudinally adjustable in a housing. 34 bolted to the outlet end donein the press, makes posof the press. An opening 35 in the housing 34 hasthe conduit 24 connected thereto, by which the discharged material isconducted to the refiner 25.

The aforementioned connector 22, or as shown in Fig. 2 another connector36 embodying a feeding vane 37, is

mounted on the press body 26 in alignment with the inlet 31. Pulpmaterial entering inlet 31 is fed through the passage 29 by a screwassembly including disconnected, axially aligned sleeves 38 and 39formed with exterial helical threads 41 and'42, respectively. A shaft 43extends through and beyond the passage 29, having a hearing at its oneend in the sleeve 33 and at its other end in a housing 44 attached tothe inlet end of the press. The sleeve 38 is rotatably mounted on theshaft 43, while the sleeve 39 is secured thereto for unison rotation.The described other end of the shaft 43 is constructed with splines 40or the like and arranged for cooperative engagement with suitable powerrotating means, while the sleeve 38 is separately rotatable as by meansincluding a sheave 45 thereon. The arrangement of parts is such that thesleeve 38 may be turned faster than the sleeve 39, thus insuring thatthat part of the screw assembly beyond the .sleeve 38 is adequatelysupplied with pulp material, the length of the sleeve 38 being short inrelation to the overall length of the screw assembly.

The sleeve 39 is formed with a longitudinal series of spaced apart,frusto conical portions 46 which may, as

indicated, be progressively greater in diameter and which in conjunctionwith the cylinder 27 define spaced apart areas 47 of low clearanceseparated by chambers 48 of relatively large clearance.

Diametrically opposed, longitudinally extending, means 49 are installedin the cylinder 27 and have longitudinally spaced apart abutments 51extending radially into the cylinder substantially in line with theportions 46, as 'Well as a pair of abutments 52 extending into thecylinder in advance of the series of portions 46.

The incoming pulp material is fed into the passage 29 by the sleeve 38and packed thereby onto the first adjacent screw threads of the sleeve39, under conditions of rising pressure. The material tends to rotatewith the sleeve 39, although this is in part inhibited by the abutments52 with the result that there is some shearing action on the pulp. Atthe same time, the material is advanced toward and into the first area47 of low clearance, retarding the rate of flow and again materiallyraising the pressure to which the material is subjected, it beingcontemplated in this connection that the developed pressures in thepress shall be on the order of six to ten thousand pounds per squareinch. Under these conditions the material is compacted in the area 47,forming in effect a plug the tendency of which to rotate with the sleeve39 is inhibited by the abutments 51. The screw threads 42 continue toforce pulp material upon such plug, and, as the forward movement of thematerial is slowed, the threads twist and partly defiber the material.The applied forces expel the compacted material from the area of lowclearance into the next adjacent chamber 48 where the high pressures areto a degree released, and then reapplied as the material is picked up bythe threads 42 and compacted into the next succeeding area 47. Thealternating cycles of compression and reduction of pressure are repeatedthroughout the series of frusto-conical portions 46, with the resultthat there is discharged from the. press a dry partly defibered materialwhich may be conducted as shown to a refiner 25 for further reduction,or used in its discharged form in the making of pressed wood boards andthe like. It is understood, in this connection, that the action of thepress is such as toexpress a substantial part of the liquid as showndiagrammatically at 50, Fig. 1, from the fibrous material (approximately70%) and also to generate added heat having a softening effect on thematerial as before described;

From the above description it will be apparent that there is thusprovided a device of the character described possessing the particularfeatures of advantage before enumerated as desirable, but whichobviously is susceptible of modification in its form, proportions,detail construction and arrangement of parts without departing from theprinciple involved or sacrificing any of its advantages. While in orderto comply with the statute the inven-' tion has been described inlanguage more or less specific as to structural features, it is to beunderstood that the invention is not limited to the specific featuresshown, but that the means and construction herein disclosed comprise butone of several-modes of putting the invention into effect, and theinvention is therefore claimed in any of its forms or modificationswithin the legitimate and valid scope of the appended claims.

Having thus described our invention, we claim:

1. In the art of pulping and refining a coarse fibrous material, amethod of, treating the fibrous material including the steps of cookingthe material at an elevated temperature on the order of 212 and higherand at a pressure on the order of 150 p.s.i. and higher, transferringthe cooked material under continued conditions of elevated temperatureand pressure to a press, and in said press squeezing said material forextraction of cooking liquid and partly defibering said material.

2. In the art of pulping and refining a coarse fibrous material, amethod of treating the fibrous material including the steps of cookingthe material under conditions of temperature on the order of 212 andhigher and at a pressure on the order of 150 p.s.i. and higher,transferring the heated material under continued conditions of elevatedpressure to a press,-said material being squeezed in said press forextraction of cooking liquid and being partly defibered, and conductingthe material from said press to a refiner for continued defibering.

3. In the art of pulping and refining, the combination of. a digester inwhich fibrous material is cooked under conditions ,of temperature andpressure elevated with respect to normal room temperature and pressure,a press having inlet and discharge ends, a connection from said digesterto said press for conducting cooked fibrous material under continuingconditions of relatively elevated temperature and pressure from saiddigester to the inlet end of said press, screw means for advancing saidmaterial through said press to said discharge end, said fibrous materialhaving residual cooking liquid expressed therefrom, and means cooperablewith said screw means for defibering the material.

4. A combination according to claim 3, characterized by a refinerconnected to the discharge end of said press and receiving the fibrousmaterial emerging therefrom.

5. In the art of pulping and refining, a press providing a throughpassage for a fibrous material, means for moving the fibrous materialthrough said passage, and means providing spaced apart low clearanceareas in said passage for intermittent compression of the fibrousmaterial. 7

6. In the art of pulping and refining, a screw press having a throughchamber and screw means rotating in said chamber, characterized bylongitudinally spaced. apart abutment means cooperating with said screwmeans to effect feed-squeeze cycles in the movement of the fibrousmaterial through said press.

7. In the art of pulping and refining, a method of treating fibrousmaterial including the steps of cooking the material, and immediatelysubjecting the material to movement through passages of low clearancewhereby to add heat to the material and promote softening of the ligninfor at least a partial defibering of the material as they pass throughsaid low clearance passages, and at the same time compressing thefibrous material -for expression of cooking liquid therefrom.

8. In the art of pulping and refining, the combination of a digester inwhich fibrous material is cooked under conditions of temperature andpressure elevated with respect to normal room temperature and pressure,said digester having an unrestricted outlet, a press having inlet andoutlet ends the former of which is in open communication with the outletof said digester to receive the cooked material while maintaining suchmaterial under the conditions of elevated temperature and pressure, andscrew means in said press feeding the material received at its inlet endto the outlet end thereof and intermittently applying squeezingpressures thereto.

9. A combination according to claim 8, characterized by a refiner inopen communication with the outlet end of said press.

10. A combination according to claim 8, characterized in that said screwmeans comprises a rotary sleeve in said press formed with disconnectedscrew threads in alternating relation to relatively large diameterportions defining with the interior of the press low clearance areasthrough which the fibrous material is forced by said screw threads.

References Cited in the file of this patent UNITED STATES PATENTS223,670 Farrell Jan. 20, 1880 1,505,934 Olier Aug. 19, 1924 1,915,812Wollenberg June 27, 1933 1,954,012 Lemberger et al Apr. 10, 19342,018,938 Wells Oct. 29, 1935 2,089,992 Campbell et al. Aug. 17, 19372,287,332 Steely June 23, 1942 2,323,194 Beveridge et al. June 29, 19432,591,106 Sutherland Apr. 1, 1952 2,616,802 Kehoe et a1 Nov. 4, 19522,663,405 Messing Dec. 22, 1953 2,673,690 Segl Mar. 30, 1954

1. IN THE ART OF PULPING AND REFINING A COARSE FIBROUS MATERIAL, AMETHOD OF TREATING THE FIBROUS MATERIAL INCLUDING THE STEPS OF COOKINGTHE MATERIAL AT AN ELEVATED TEMPERATURE ON THE ORDER OF 212* AND HIGHERAND AT A PRESSURE ON THE ORDER OF 150 P.S.I. AND HIGHER, TRANSFERRINGTHE COOKED MATERIAL UNDER CONTINUED CONDIDTIONS OF ELEVATED TEMPERATUREAND PRESSURE TO A PRESS, AND IN SAID PRESS SQUEEZING SAID MATERIAL FOREXTRACTION OF COOKING LIQUID AND PARTLY DEFIBERING SAID MATERIAL.